1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to a structure for accommodating different types of image forming units in an apparatus main body.
2. Description of the Related Art
A conventional image forming apparatus includes an image forming unit for forming an image on a sheet. The image forming unit includes elements such as an image writing unit including a laser scanner and an LED array, a photosensitive drum, primary and secondary chargers, a toner supply unit, a transfer unit, a toner collecting/cleaning unit, an image fixing unit, a drive unit, and a sheet conveying unit.
As examples of the image forming unit, there are known an image forming unit of a monochromatic electrophotographic system using one photosensitive drum, an image forming unit of a tandem-type color electrophotographic system using a plurality of photosensitive drums arranged in series, and an image forming unit of a rotary-type color electrophotographic system using a plurality of photosensitive drums to be rotated.
Up to now, there is one type of an image forming apparatus from which an image forming unit can be removed to an outside to be, for example, replaced with another image forming unit or repaired when a life of the image forming unit comes to an end. In the image forming apparatus, for example, an indication is given when the replacement of the imaging unit serving as a component of the image forming unit is required because of the end of the life thereof, and the imaging unit and the photosensitive drum are detachably mounted on the apparatus main body. Japanese Patent Application Laid-Open No. 64-26865 discloses an example of the image forming apparatus having such a structure.
In the conventional image forming apparatus including the image forming unit mounted in a replaceable manner, the replacement or the like of the image forming unit is possible. However, the image forming apparatus is not ready for a wide variety of the products (image forming unit) manufactured in recent years. In other words, while there are various image forming units using the electrophotographic systems mentioned above in a case where the electrophotographic systems to be used in the image forming units are different from each other, a position and direction into which a sheet enters and a position and direction into which a sheet is discharged are also different. In addition, a position of a heat source such as a fixing device, conditions of airflow (air pressure gradient) by the components are different from one system to another.
For this reason, it is difficult to entirely remove the image forming unit from the apparatus main body to incorporate another image forming unit having a different structure in the apparatus main body. Therefore, when, for example, the apparatus main body is recovered and a frame of the apparatus main body, that is, a support of the image forming unit is to be recycled, it is necessary to individually design the support in compliance with the type of an image forming unit to be newly incorporated in the apparatus main body.
Specifically, in the conventional image forming apparatus, even when the apparatus main body is to be recycled by replacing the image forming unit with another image forming unit, it is difficult to receive an image forming unit having a different structure from that of the image forming unit used until being recovered, in the apparatus main body. As a result, reuse of (the frame of) the apparatus main body or common use thereof cannot be achieved. Further, in a case where one apparatus main body is reused by another apparatus, there are problems in that, for example, a large number of designing steps are required, and management costs for the recycling are increased.